The projection of the olfactory bulb in opossum to the neopallial part of insula cortex was established using the cupric-silver method for detecting degeneration. To confirm this projection, horseradish peroxidase (HRP) was injected into the olfactory bulb of opossum. The anterograde movement of the HRP was detected using a new, more sensitive, histochemical procedure. This procedure allowed visualization of the HRP reaction product in axon terminals present in the same areas where degenerating terminals had been found, including the neopallial part of the insula cortex.